Outburst floods along the Columbia River (fieldtrip lead by Jim O'Connor)

Overtopping of lakes and outburst floods.

Large tectonic lakes which water level overtops the surrounding topography can trigger megafloods, as recorded in the Pleistocene Lake Bonneville. These floods are comparable in magnitude to outburst floods produced by collapsing ice barriers blocking rivers (see pictures from the Altay 2010 field trip, to the right), and they leave a significant erosional imprint in the geomorphology of the outlet. I explain some more in this blog.

Interplay between tectonics, climate, and fluvial transport during the evolution of tectonic lakes and internally-drained basins.

On geological time scales, lakes are ephemeral water bodies that, as the mechanism generating the topographic basin ceases, disappear by erosion along their outlet and/or overfill with sediments brought by tributaries. Therefore, the evolution of a lake and the potential formation of a closed (internally-drained, endorheic) basin depend both on tectonic and climatic factors. How does climate affect the life of a lake at long time-scales? Is the evaporation at the lake's surface as relevant as the tectonic uplift generating the lake? What are the tectonic/climatic conditions under which a lake develops and what are the ones under which a lake becomes internally-drained? These questions are addressed via computer simulations incorporating physico-mathematical approaches to the processes of tectonic uplift and river erosion.

This animation is an example of a cross-section computer simulation of the evolution of a lake created by tectonic uplift across an river profile initially in equilibrium. The horizontal axis corresponds to distance along the river flow. This evolution has been calculated using the software tAo assuming a constant precipitation and evaporation rate through the entire domain, an uplift rate of 2 mm/yr during the 1st million years, and a transport capacity proportional to water discharge and slope.
Bedrock in brown, sediments in yellow, water in blue. Time is indicated in millions of years.Note that the closure of the lake (when evaporation in the lake surface compensates the water collected upstream and therefore the output water decreases to 0) occurs at 0.6 Myr, and the abrupt opening by lake capture(due to the regressive erosion at the escarpment to the right) occurs at 1.7 Myr.